In malignant tumors, the cells proliferate, grow rapidly and move to other parts of the body to form new tumors. This stage of disease is called.

Options

A. metagenesis
B. metastasis
C. teratogenesis
D. mitosis

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Malignant Tumors**: Malignant tumors are characterized by the uncontrolled and excessive growth of cells. Unlike benign tumors, which remain localized, malignant tumors can invade surrounding tissues.

2. **Proliferation and Growth**: In malignant tumors, the cancerous cells not only proliferate (increase in number) but also grow rapidly. This rapid growth is a hallmark of cancer.

3. **Invasion of Adjacent Tissues**: Malignant tumors invade adjacent tissues, which means they spread into neighboring areas and disrupt normal tissue function.

4. **Metastasis**: One of the most critical aspects of malignant tumors is their ability to spread to other parts of the body. This occurs when cancerous cells enter the bloodstream or lymphatic system and travel to distant sites, where they can form new tumors.

5. **Defining the Stage**: The process of spreading from the original tumor site to other parts of the body is specifically termed "metastasis." This is a key stage in the progression of malignant tumors and is associated with a more severe prognosis.

6. **Distinguishing from Other Terms**: It’s important to differentiate metastasis from similar-sounding terms like "metagenesis," which is unrelated to cancer and refers to a biological process in certain lower animals.

**Final Answer**: The stage of disease in malignant tumors where cells proliferate, grow rapidly, and move to other parts of the body to form new tumors is called **metastasis**.

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